Method and system for determining the state of a drilling operation

ABSTRACT

A method for determining a state of a drilling operation includes providing a first set of operational data of the drilling operation through a first time interval, providing a set of operational event dividers that delimit a plurality of second time intervals within the first time interval, for at least one of the plurality of second time intervals, providing a second set of operational data of the drilling operation through a second time interval, deriving characteristic values of the second set of operational data through the second time interval, and determining the state of the drilling operation in the second time interval based on the characteristic values.

CROSS REFERENCE TO PRIOR APPLICATIONS

Priority is claimed to Norwegian Patent Application No. 20151585, filed Nov. 19, 2015. The entire disclosure of said application is incorporated by reference herein.

FIELD

The present invention relates to a method, a computer program product, and a system for determining the state of a drilling operation.

BACKGROUND

Automatically identifying the state of a drilling operation, for example, in petroleum exploration, is challenging due to a number of factors which include the high number of possible process states (e.g., drilling, tripping in or out, flow checks, sliding, and bore hole conditioning), the fact that parameters may quickly change, certain parameters that are not directly observable, and because measured signals may contain noise or invalid readings.

U.S. Pat. No. 6,892,812 describes a method for determining the state of a well operation, wherein measured process data is checked for validity before being used to determine the state. WO 2014/160561 A1 describes a method for automatically generating a drilling rig activity report while operating the rig. US 2015/0167392 A1 describes methods for determining the drilling state of a downhole tool and controlling the trajectory of the downhole tool in a wellbore during a drilling operation.

In many cases, data may be erroneous or not represent the actual operating variable accurately, but still be within a range which would be representative for an actual drilling operation. For example, a measured torque and rotation of the drill string to spin in and connect a section of the drill string may be indistinguishable from the start of an actual drilling process. There is therefore a need for improved methods and systems for identifying the state of a drilling operation based on measured process parameters.

SUMMARY

An aspect of the present invention is to provide an improved method and system, and to obviate at least some disadvantages of prior art techniques.

In an embodiment, the present invention provides a method for determining a state of a drilling operation which includes providing a first set of operational data of the drilling operation through a first time interval, providing a set of operational event dividers that delimit a plurality of second time intervals within the first time interval, for at least one of the plurality of second time intervals, providing a second set of operational data of the drilling operation through a second time interval, deriving characteristic values of the second set of operational data through the second time interval, and determining the state of the drilling operation in the second time interval based on the characteristic values.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows an example of sequences in a drilling operation;

FIG. 2 shows extracts of the data shown in FIG. 1 and its use in a method for determining the state of a drilling operation;

FIG. 3 shows extracts of the data shown in FIG. 1 and its use in a method for determining the state of a drilling operation;

FIG. 4 shows sequences in a drilling operation and their use in a method for determining the state of a drilling operation; and

FIG. 5 is a schematic flow chart illustrating a method for determining the state of a drilling operation.

DETAILED DESCRIPTION

A drilling operation comprises a number of different operations and states, such as drilling (“making hole”), connection, reaming, trip in, trip out, etc. Numerous process variables are usually measured and logged during the drilling operation. FIG. 1 shows an example of sequences in a drilling operation. FIG. 1 thereby shows a number of logged process variables for the drilling operation, plotted against time. As is explained in further detail below, FIG. 1 generally shows one drilling connection sequence A, one drilling sequence B, and one drilling connection sequence C.

FIG. 1 shows: slips state 1, where a value 0 indicates slips open and a value 1 indicates slips closed; weight-on-bit (WOB) 2, i.e., the weight acting on the drill bit; rotation 3, i.e., the rotational speed of the drill string; mud flow rate 4; torque 5, i.e., the torque applied to the drill string; and bit depth 6, i.e., the depth of the drill bit in the borehole.

The values for the process variables 1-6 can be obtained in a number of different ways, e.g., by direct measurement (e.g., sensors), or indirectly by the use of other operational parameters obtained from the drilling equipment. For example, mud flow can be obtained by direct flow measurements, or indirectly via the rotational speed of the mud pumps. Weight-on-bit can similarly be measured or calculated from hook load, while taking into account drill string weight. The detailed manner in which these process variables are obtained is not significant for the present invention.

For the purpose of, among other things, analyzing the drilling operation, it is desirable to identify and differentiate between the different sub-operations, or states, carried out during the drilling operation.

According to the present invention, there is provided a method for determining the state of a drilling operation. FIGS. 2 and 3 show extracts of the data shown in FIG. 1, i.e., a set of historical operational data for a drilling operation over a defined first time interval. This data may be provided from a data logger in a drilling management system.

An event divider is provided, whereby the weight-on-bit falling below or increasing above a threshold level WOB_(th) will delimit the operational data into a plurality of time intervals. It can be seen in FIG. 1 that weight-on-bit falling below the threshold at time t₁ to weight-on-bit increasing above the threshold at time t₂ provides one time interval t₁ to t₂. A further event divider similarly exists at the time where weight-on-bit again drops below the threshold (see FIG. 3) defining a second time interval t₂ to t₃. A plurality of second time intervals can thus be defined for the set of operational data.

For at least one of these plurality of time intervals, at least part of the operational data falling within that time interval is selected for further analysis. This may include readings for the process variables 1-6. This step will now be explained in relation to FIG. 3 and the time interval t₂ to t₃, however, the step could be performed equivalently for the time interval t₁ to t_(2.)

Over the time interval, characteristic values of one or more of the process variables may be derived. The characteristic values may include an average value of the process variable over the time interval, a median value over the time interval, or a change in the process variable over the time interval.

For the process variables shown in FIG. 3, characteristic values may include the average value over the time period for: Rotation, R_(avg); Flow, F_(avg); and Torque, T_(avg). They may further include the change in bit depth over the period, ABD.

The characteristic values can be used to determine the state of the drilling operation for that time interval by comparing the characteristic values with pre-determined threshold values. For example, one may define threshold levels R_(threshold), F_(threshold) and T_(threshold) for the rotation, flow and torque levels, respectively. If the characteristic value for the relevant process variable is above the threshold value for that time period, then one can consider that process variable to be “true” or “on”.

By using simple logic or a look-up table, one can then, on the basis of the characteristic values and the threshold(s), determine the state of the drilling operation. For example, to identify a drilling sequence (i.e., “making hole”) such as the one shown in FIG. 3 (time interval t₂ to t₃), the method would identify a time interval starting with an event divider WOB becoming “true” (i.e., the logged weight-on-bit increasing above the threshold value) and ending with WOB becoming “false”, and with characteristic values during that time interval indicating that flow F, rotation R, and torque T, are “on”, while the change in bit depth, ABD, is above some threshold value, e.g., 5 m. This is illustrated in Table 1.

TABLE 1 Event Dividers Characteristic Value State Activity Start End ΔBD F R T Drilling WOB = True WOB = False >5 m On On On Drilling Connection WOB = False WOB = True <5 m — Off Off

Similarly, the time interval shown in FIG. 2 (t₁ to t₂) could be identified as a drilling connection sequence.

In an embodiment of the present invention, the process variable (or variables) used as event dividers can, for example, be included in the operational data. The process variable (or variables) used as event dividers may also be used to determine characteristic values used to determine the state of the drilling operation. For example, the weight-on-bit may be used as a characteristic value, whereby weight-on-bit is considered to be “on” if above a pre-determined threshold value. (This threshold value may be different from the threshold value, WOB_(th), used for event divider purposes.)

In an embodiment of the present invention, the method can, for example, use more than one process variable as event dividers. This allows more granularity in the analysis, and thus may give higher accuracy. The number of event dividers can be determined according to the specific needs in any one case. For example, in addition to weight-on-bit, the slips state can be used as event dividers. This is illustrated in FIG. 4 in which event dividers t_(a-d) delimit time periods t_(a)-t_(b) (WOB false to slips close), t_(b)-t_(c) (slips close to slips open), and t_(c)-t_(d) (slips open to WOB true). By defining several event dividers, it is thus possible to identify a larger number of different sub-processes during the drilling operation. An example of a look-up table for use in such a case is shown in Table 2.

TABLE 2 Process Variable State Event Dividers Slips Activity Start End ΔBD WOB F R T State Drilling WOB = True WOB = False  >5 m On On On On 0 Drilling WOB = False WOB = True  <5 m Off — Off Off 1 Connection Reaming Slips Open WOB = True >10 m Off On On — 1 & Bit Depth = Hole Depth Trip In Slips Close Slips Close >Stand Off Off Off Off 1 Length −20% Trip Out Slips Close Slips Close <−Stand Off Off Off Off 1 Length −20% Back WOB = False Slips Close <−Stand Off On On — 1 Reaming Length −20% Trip In Slips Close Slips Close >0 & <pipe Off Off Off Off 1 Singles length Trip Out Slips Close Slips Close <0 & >−pipe Off Off Off Off 1 Singles length Wet Trip In Slips Close Slips Close >Stand Off On Off Off 1 Length −20% Wet Trip Out Slips Close Slips Close <−Stand Off On Off Off 1 Length −20%

An exemplary embodiment of the method has been illustrated by the schematic flow chart in FIG. 5. The method 100 is a method for determining a state of a drilling operation.

The method starts at the initiating step 110.

First, the operational data provision step 120 is performed. Step 120 includes providing a first set of operational data of the drilling operation through a first time interval. The operational data typically include status data obtained by drilling equipment or operational measurements provided by sensors. The first set of operational data may, for example, be selected from weight-on-bit, mud circulation rate, rotation, torque, slips state, and bit depth.

The first set of operational data may, for example, include all of weight-on-bit, mud circulation rate, rotation, torque, slips state, and bit depth.

The provided operational data may include process variables provided directly (e.g., from sensors), or indirectly. For example, if the operational data includes mud circulation rate, or mud flow, this may be provided either directly by flow measurement equipment or indirectly by monitoring a rotational speed of a mud pump. This has been further elaborated in the above detailed description, for example, with reference to FIG. 1 above.

Next, in the event divider provision step 130, a set of operational event dividers that delimit a plurality of second time intervals is provided within the first time interval.

The operational event dividers may advantageously be provided so that the plurality of second time intervals do not overlap. More specifically, the operational event dividers may advantageously be provided so that the plurality of second time intervals span the entire first time interval.

The operational event dividers may advantageously represent points of time, whereby values of data that are included in the operational data cross a predetermined threshold value.

For example, an event divider may represent the point of time whereby a weight-on-bit signal exceeds a predetermined threshold value, or drops below a predetermined threshold value. This has been further elaborated in the above detailed description, for example, with reference to FIGS. 2 and 3 above.

The operational event dividers may, for example, be selected from the following events: slips open, slips close, weight-on-bit on, weight-on-bit off. Other operational event dividers are also possible.

The second time interval may, for example, be delimited by operational event dividers that represent data of a same class of operational data. A class of operational data may be a set of operational data that represents the same physical entity. For example, weight-on bit may represent one class of operational data, while slips state may represent another class of operational data.

The second time interval may, for example, be delimited by a first event divider which represent weight-on-bit on and a second event divider which represent weight-on-bit off, or vice versa. Alternatively, the second time interval may, for example, be delimited by a first event divider which represent slips open, and a second event divider which represent slips closed, or vice versa. The same class of operational data is used for delimiting the second time interval in any of these exemplary cases. This has been further elaborated in the above detailed description, for example, with reference to FIGS. 2 and 3 above.

The second time interval may alternatively be delimited by operational event dividers which represent data of different classes of operational data. In such a case, the second time interval may, for example, be delimited by a first event divider which represent weight-on-bit off, and a second event divider which represent slips close. In this case, different classes of operational data are used for delimiting the second time interval. This principle has been further elaborated and exemplified in the above detailed description, for example, with reference to FIG. 4 and Table 2 above.

Referring again to the flow chart of FIG. 5, the next step 140 is another operational data provision step which is performed for at least one of the second time intervals delimited by the event dividers provided in step 130. Step 140 includes providing a second set of operational data of the drilling operation through the second time interval.

The types of operational data provided in step 140 may be a subset of the types of operational data provided in step 120. The operational data provided in step 140 may alternatively be the same operational data as those provided in step 120.

As an example, when the first set of operational data includes all of weight-on-bit, mud circulation rate, rotation, torque, slips state, and bit depth, the second set of operational data may include the subset consisting of mud circulation rate, rotation, and torque. Numerous other examples are possible. This has been further elaborated in the above detailed description, for example, with reference to FIG. 3 above.

Further, in step 150, characteristic values of the second set of operational data are derived through the second time interval.

The characteristic values of the second set of operational data through the second time interval may advantageously be calculated as an average of the operational data through the second time interval.

The characteristic values of the second set of operational data through the second time interval may alternatively be calculated as a median of the operational data through the second time interval, or as a change in the operational data over the second time interval.

As an example, average values of mud circulation rate, rotation, and torque may be calculated as characteristic values in step 150. Numerous other examples are possible. This has been further elaborated in the above detailed description, for example, with reference to FIG. 3 above.

Next, in step 160, the state of the drilling operation in the second time interval is determined, based on the characteristic values.

Step 160 of determining the state of the drilling operation based on the characteristic values may advantageously include comparing the characteristic values with predetermined threshold values.

Step 160 of determining the state of the drilling operation based on the characteristic values can, for example, include looking up in pre-stored data. The predetermined threshold values may in this case be kept as pre-stored data in a lookup-table, such as Table 1 or Table 2 referred to in the detailed description above.

In an embodiment of the present invention, the step 140 of providing a second set of operational data of the drilling operation through the second time interval, the step 150 of deriving characteristic values of the second set of operational data through the second time interval, and the step 160 of determining the state of the drilling operation based on the characteristic values, may be repeated for the plurality of second time intervals that are delimited by event dividers provided in step 130. This results in a series of determined states of the drilling operation through the first time interval.

In an embodiment of the present invention, the step 120 of providing a first set of operational data of the drilling operation through a first time interval is completed before the performance of step 130 of providing a set of operational event dividers, step 140 of providing a second set of operational measurements, step 150 of deriving characteristic values, and the step 160 of determining the state of the drilling operation. This results in the state of the drilling operation being determined as a post-processing analysis, after the completion of the operational data acquisition in step 120. This approach differs substantially from real-time processing of acquired operational data.

The illustrated method ends at the terminating step 190.

The method may advantageously be implemented as a computer-implemented method. A computer program product is provided in this case which, when loaded into a memory and executed on a processing device, causes the processing device to perform a method as disclosed herein.

The method may also be implemented in a system for determining a state of a drilling operation. Such a system comprises input devices for providing operational data of the drilling operation, and a computer device which is configured to perform a method as disclosed herein. More specifically, the computer device may include a processing device and a memory, the memory being arranged to hold a computer program that causes the processing device to perform a method as disclosed herein when the computer program is executed by the processing device.

The disclosed method, computer program product, and system may permit an accurate determination of the state of a drilling operation with less sensitivity to, for example, erroneous or noisy data, or natural variations (for example, torsional vibrations in the drill string producing short torque peaks). In practice, one may have situations where the process variables at a particular time indicate that a different sequence has commenced. A method considering the instantaneous values of the process variables to identify the state of a drilling operation may therefore produce false predictions. The method according to the present invention determines the state of a drilling operation more accurately and for the full time period considered.

According to the disclosed method, computer program product, and system, the event dividers can further be based on data which are included in the operational data. That allows the plurality of second time intervals to be defined on the basis of the actual drilling operation, i.e., according to what the drilling plant actually carried out. This may be different from what is commanded by the driller because time delays max exist between a command sent to carry out some operation and when the operation actually starts. It is beneficial to base such calculations on actual operations in order to determine performance parameters accurately (for example, rate of penetration during drilling).

By determining and storing drilling operation state and activities as statistical parameters (instead of the full logged data set), one also facilitates data transfer (for example, to shore) and storage, while maintaining the granularity of having accurate data to identify the operation for relevant individual time windows.

The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 

What is claimed is:
 1. A method for determining a state of a drilling operation, the method comprising: providing a first set of operational data of the drilling operation through a first time interval; providing a set of operational event dividers that delimit a plurality of second time intervals within the first time interval; for at least one of the plurality of second time intervals, providing a second set of operational data of the drilling operation through a second time interval; deriving characteristic values of the second set of operational data through the second time interval; and determining the state of the drilling operation in the second time interval based on the characteristic values.
 2. The method as recited in claim 1, wherein the operational data is selected from at least one of status data obtained by drilling equipment and an operational measurement provided by a sensor.
 3. The method as recited in claim 1, wherein the operational data is selected from at least one of a weight-on-bit, a mud circulation rate, a rotation, a torque, a slips state, and a bit depth.
 4. The method as recited in claim 1, wherein the set of operational event dividers are provided so that the plurality of second time intervals do not overlap.
 5. The method as recited in claim 4, wherein the set of operational event dividers are provided so that the plurality of second time intervals span the entire first time interval.
 6. The method as recited in claim 1, wherein, the set of operational event dividers represent points of time, and the operational data comprises values of data which cross a predetermined threshold value.
 7. The method as recited in claim 1, wherein the set of operational event dividers are selected from at least one of a slips open event, a slips close event, a weight-on-bit on event, and a weight-on-bit off event.
 8. The method as recited in claim 1, wherein the second time interval is delimited by operational event dividers representing data of a same class of operational data.
 9. The method as recited in claim 1, wherein the second time interval is delimited by operational event dividers representing data of a different class of operational data.
 10. The method as recited in claim 1, wherein the characteristic values of the second set of operational data through the second time interval are derived as, an average of the second set of operational data through the second time interval, a median of the second set of operational data through the second time interval, or a change in the second set of operational data over the second time interval.
 11. The method as recited in claim 1, wherein the step of determining the state of the drilling operation based on the characteristic values includes comparing the characteristic values with at least one predetermined threshold value.
 12. The method as recited in claim 1, wherein the step of determining the state of the drilling operation based on the characteristic values includes looking up in prestored data.
 13. The method as recited in claim 1, wherein, the step of providing the second set of operational data of the drilling operation through the second time interval, the step of deriving characteristic values of the second set of operational data through the second time interval, and the step of determining the state of the drilling operation in the second time interval based on the characteristic values, are repeated for the plurality of second time intervals so as to result in a series of determined states of the drilling operation through the first time interval.
 14. The method as recited in claim 1, wherein the step of providing the first set of operational data of the drilling operation through the first time interval is completed before each of, the step of providing the set of operational event dividers, the step of providing a second set of operational data, the step of deriving characteristic values, and the step of determining the state of the drilling operation.
 15. A computer program product which, when loaded into a memory and executed on a processing device, causes the processing device to perform the method as recited in claim
 1. 16. A system for determining a state of a drilling operation, the system comprising: input devices configured to provide operational data of the drilling operation; and a computer device configured to perform the method recited in claim
 1. 